Commit 4b6c1060 authored by Heinz Mauelshagen's avatar Heinz Mauelshagen Committed by Shaohua Li
Browse files

md: fix md_write_start() deadlock w/o metadata devices 

If no metadata devices are configured on raid1/4/5/6/10
(e.g. via dm-raid), md_write_start() unconditionally waits
for superblocks to be written thus deadlocking.

Fix introduces mddev->has_superblocks bool, defines it in md_run()
and checks for it in md_write_start() to conditionally avoid waiting.

Once on it, check for non-existing superblocks in md_super_write().

Link: https://bugzilla.kernel.org/show_bug.cgi?id=198647


Fixes: cc27b0c7 ("md: fix deadlock between mddev_suspend() and md_write_start()")

Signed-off-by: default avatarHeinz Mauelshagen <heinzm@redhat.com>
Signed-off-by: default avatarShaohua Li <sh.li@alibaba-inc.com>
parent b126194c

drivers/md/md.c

+10 −0
Original line number Diff line number Diff line
@@ -801,6 +801,9 @@ void md_super_write(struct mddev *mddev, struct md_rdev *rdev, 
	struct bio *bio;

	int ff = 0;



	if (!page)

		return;



	if (test_bit(Faulty, &rdev->flags))

		return;
@@ -5452,6 +5455,7 @@ int md_run(struct mddev *mddev) 
	 * the only valid external interface is through the md

	 * device.

	 */

	mddev->has_superblocks = false;

	rdev_for_each(rdev, mddev) {

		if (test_bit(Faulty, &rdev->flags))

			continue;
@@ -5465,6 +5469,9 @@ int md_run(struct mddev *mddev) 
				set_disk_ro(mddev->gendisk, 1);

		}



		if (rdev->sb_page)

			mddev->has_superblocks = true;



		/* perform some consistency tests on the device.

		 * We don't want the data to overlap the metadata,

		 * Internal Bitmap issues have been handled elsewhere.
@@ -8065,6 +8072,7 @@ EXPORT_SYMBOL(md_done_sync); 
bool md_write_start(struct mddev *mddev, struct bio *bi)

{

	int did_change = 0;



	if (bio_data_dir(bi) != WRITE)

		return true;
@@ -8097,6 +8105,8 @@ bool md_write_start(struct mddev *mddev, struct bio *bi) 
	rcu_read_unlock();

	if (did_change)

		sysfs_notify_dirent_safe(mddev->sysfs_state);

	if (!mddev->has_superblocks)

		return true;

	wait_event(mddev->sb_wait,

		   !test_bit(MD_SB_CHANGE_PENDING, &mddev->sb_flags) ||

		   mddev->suspended);

drivers/md/md.h

+2 −0
Original line number Diff line number Diff line
@@ -468,6 +468,8 @@ struct mddev { 
	void (*sync_super)(struct mddev *mddev, struct md_rdev *rdev);

	struct md_cluster_info		*cluster_info;

	unsigned int			good_device_nr;	/* good device num within cluster raid */



	bool	has_superblocks:1;

};



enum recovery_flags {

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